Voltage and Frequency Control of Self Excited Induction Generator Feeding Stand-Alone AC Loads

There has been a growing use of Induction Machines (IMs) in wind power generation schemes, particularly for supplying electrical power in remote areas. A Squirrel-Cage Induction Generator (SCIG) is preferred over Slip Ring Type Induction Generator (SRIG) due to its several advantages for stand-alone applications, such as no need for an external power supply to produce magnetic field, less maintenance, simple and rugged construction, and brushless rotor type. But the main disadvantage of Squirrel-Cage Induction Generator (SCIG) is its poor voltage and frequency for changes in rotor speed and load. This paper proposes an open-loop reactive power compensator scheme for controlling the voltage and frequency of a wind-turbine driven self-excited induction generator for low power stand-alone applications. The scheme comprises of one set of fixed capacitor bank and a parallel connected three-phase fixed frequency Pulse Width Modulation (PWM) inverter fed from a battery connected across the stator terminals of a three-phase squirrel cage induction generator. This system inherently adapts to the changes in rotor speed or load on the generator while maintaining a near constant voltage and frequency at the load terminals.